Power transmitting apparatus, method of controlling the same, and power transmission system

ABSTRACT

Foreign substance detection can be performed with a simple configuration in a power transmission system. A power transmitting apparatus that wirelessly transmits power to a power receiving apparatus, the power transmitting apparatus comprises: determination means for, in a case where an initial impedance value and the detected output impedance value do not match and there is no change in the output impedance value between before and after the transmission of a predetermined detection signal, determining that a foreign substance is present within a predetermined power transmission range, and, in a case where the initial impedance value and the detected output impedance value do not match and there is a change in the output impedance value between before and after the transmission of the predetermined detection signal, determining that a power receiving apparatus is present within the predetermined power transmission range.

TECHNICAL FIELD

The present invention relates to a wireless power transmissiontechnique.

BACKGROUND ART

In recent years, wireless power transmission systems have undergonebroad technical development. Incidentally, if a foreign substance suchas a piece of metal is present in the range in which a powertransmitting apparatus can transmit power, an eddy current will flow inthe foreign substance and unintended heating will occur. For thisreason, in a wireless power transmission system, it is necessary toperform appropriate power transmission to a power receiving apparatuswhile giving consideration to the influence on foreign substances. Forexample, Japanese Patent Laid-Open No. 2013-17379 (Patent Literature 1)proposes a technique of providing a power receiving apparatus with acircuit for measuring the Q-value of the power receiving antenna andperforming foreign substance detection using the Q-value measurementresult.

However, in the technique disclosed in Patent Document 1 above, there isa problem in that the circuit for measuring the Q-value of the powerreceiving antenna needs to be newly provided and the cost will increase.

SUMMARY OF INVENTION

According to an aspect of the present invention, a power transmittingapparatus that wirelessly transmits power to a power receivingapparatus, the power transmitting apparatus comprises: powertransmission means for performing wireless power transmission to a powerreceiving apparatus arranged within a predetermined power transmissionrange; storage means for storing an initial impedance value that is anoutput impedance value of the power transmission means in a state whereno object is present within the predetermined power transmission range;detection means for detecting the output impedance of the powertransmission means when a predetermined detection signal has beentransmitted by the power transmission means; and determination meansfor, in a case where the initial impedance value and the outputimpedance value detected by the detection means do not match and thereis no change in the output impedance value between before and after thetransmission of the predetermined detection signal, determining that aforeign substance is present within the predetermined power transmissionrange, and, in a case where the initial impedance value and the outputimpedance value detected by the detection means do not match and thereis a change in the output impedance value between before and after thetransmission of the predetermined detection signal, determining that apower receiving apparatus is present within the predetermined powertransmission range.

According to an aspect of the present invention, it is possible toprovide a technique that enables foreign substance detection using asimple configuration and enables appropriate power transmission controlin a power transmission system.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention and,together with the description, serve to explain the principles of theinvention.

FIG. 1 is a diagram of an overall configuration of a power transmissionsystem according to a first embodiment.

FIGS. 2A to 2D are diagrams showing examples of states in the peripheryof a power transmission range in the power transmission system.

FIG. 3 is a diagram for describing an operation of a detection unit 103.

FIG. 4 is a diagram showing an exemplary configuration of a class-Eamplifier.

FIG. 5 is a timing diagram for describing operations of a powertransmission unit 113 and the detection unit 103.

FIGS. 6A and 6B are timing diagrams for describing operations of a powertransmitting apparatus.

FIG. 7 is a diagram showing an example of flags stored in a system statestorage unit 105.

FIG. 8 is a diagram showing an example of information stored in an IDstorage unit 106 in the power transmitting apparatus.

FIG. 9 is a diagram showing an example of information stored in an IDstorage unit 121 in a power receiving apparatus.

FIGS. 10A and 10B are flowcharts of operations of the detection unit103.

FIGS. 11A and 11B are flowcharts of operations for BT control in a powertransmitting apparatus 100.

FIGS. 12A and 12B are flowcharts of operations for power transmissioncontrol in the power transmitting apparatus 100.

FIGS. 13A and 13B are flowcharts of operations for BT control in a powerreceiving apparatus 101.

FIGS. 14A and 14B are flowcharts of operations for power receptioncontrol in the power receiving apparatus 101.

FIG. 15 is a diagram showing an example of information stored by animpedance storage unit 110.

DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention will be described indetail below with reference to the drawings. Note that the embodimentsbelow are merely examples and are not intended to limit the scope of thepresent invention.

First Embodiment

A first embodiment of a power transmission system according to thepresent invention will be described below using, as an example, awireless power transmission system including a power transmittingapparatus 100 that performs wireless power transmission and a powerreceiving apparatus 101.

Configuration of Apparatuses

FIG. 1 is a diagram of the overall configuration of the powertransmission system according to the first embodiment. The powertransmitting apparatus 100 and the power receiving apparatus 101 performpower transmission via a medium 102. Note that the power transmittingapparatus and the power receiving apparatus exchange control informationthat is to be used for wireless power transmission control viacommunication units included in both apparatuses, and this will bedescribed in detail later. For this reason, control for establishing anddisconnecting a communication channel between the power transmittingapparatus and the power receiving apparatus will also be described.

The configuration of the power transmitting apparatus 100 will bedescribed first. A detection unit 103 is a functional unit that performsdetection of an output impedance value (referred to as “Z-detection”below) of a DC voltage source 401 in a class-E amplifier thatconstitutes a power transmission unit 113, and will be described indetail later. A control unit 104 is a functional unit that controls thepower transmitting apparatus 100 according to the detection result ofthe detection unit 103. A system state storage unit 105 is a functionalunit that stores states of the power transmission system and will bedescribed in detail later with reference to FIG. 7 . An ID storage unit106 is a functional unit that stores identification information of thepower receiving apparatus 101 and will be described in detail later withreference to FIG. 8 .

A first timer 107, a second timer 108, and a third timer 109 are timersthat are used as appropriate according to the system operation state andwill be described in detail later. An impedance storage unit 110 is afunctional unit that stores results of impedance value detectionperformed by the detection unit 103 and will be described in detaillater with reference to FIG. 15 . An error cancel switch 111 is afunctional unit that receives a user operation, for example, in order tocancel a system error state. A display unit 112 is a functional unitthat displays information regarding the wireless power transmissionsystem, and displays error information for example.

The power transmission unit 113 supplies power to be transmitted via themedium 102 to a power transmitting antenna 115. Here, the powertransmission unit 113 is described as being constituted by a class-Eamplifier. A resonance control unit 114 is a functional unit thatcontrols the resonance frequency and characteristic impedance of thetransmission channel that is constituted by a power transmitting antenna115, the power receiving antenna 125, and the medium 102.

A communication unit 116 (power transmitting apparatus communicationmeans) is a functional unit that exchanges control signals regardingpower that is to be transmitted between the power transmitting antenna115 and the power receiving antenna 125. Note that the control signalsare exchanged via antennas for communication (not shown). In the firstembodiment, the communication unit 116 is compatible with a Bluetooth(registered trademark) standard (referred to as “BT” below), but it maybe compatible with another communication standard. Also, here, thecommunication unit 116 functions as a BT-standard master device. Inaddition, the power transmitting apparatus 100 is configured to use SDP(Service Delivery Protocol) to announce services that it provides toperipheral devices, and this will be described in detail later. Here,the power transmitting apparatus 100 announces that it provides aservice called “Wireless Charger”.

The configuration of the power receiving apparatus 101 will be describednext. A power reception unit 117 is a functional unit that receivespower transmitted from an external apparatus (here, the powertransmitting apparatus 100). A load 118 consumes power received by thepower reception unit 117, and it is constituted by a charge circuit anda battery here. A communication unit 119 (power receiving apparatuscommunication means) is a functional unit that exchanges control signalsregarding power that is to be transmitted between the power transmittingantenna 115 and the power receiving antenna 125. It is compatible withthe BT standard, similarly to the communication unit 116. Here, thecommunication unit 119 is described as functioning as a BT-standardslave device.

A comparing unit 120 is a functional unit that compares informationreceived by the power receiving antenna 125 and information received bythe communication unit 119. An ID storage unit 121 stores informationreceived by the power receiving antenna 125 and identificationinformation for the power transmitting apparatus 100 that is receivedusing the communication unit 119. A fourth timer 122 and a fifth timer123 are timers that are used as appropriate according to the systemoperation state, and will be described in detail later.

A display unit 124 is a functional unit that displays informationregarding the wireless power transmission system, and displays errorinformation for example. The power receiving antenna 125 is a functionalunit that electromagnetically couples with the power transmittingantenna 115 and receives power. A switching unit 126 is a functionalunit that connects the power receiving antenna 125 to a resonance unit128 or a high resistance 127.

The high resistance 127 is a constant resistance of around severalmegaohms, for example. It has a configuration in which the impedance ofthe power receiving antenna 125 seen by the power transmitting antenna115 becomes a high impedance (referred to as “Hi-Z” below) when thepower receiving antenna 125 and the high resistance 127 are connected.Note that approximately no current flows in the power receiving antenna125 when the impedance is set to Hi-Z.

The resonance unit 128 is a functional unit for causing the powertransmission channel to resonate at a specific impedance. Here, thepower transmission channel is constituted by the resonance control unit114, the power transmitting antenna 115, the medium 102 that is to bethe transmission channel, and the power receiving antenna 125. Note thata characteristic impedance 129 is a characteristic impedance in the casewhere the resonance circuit is seen by a load switching unit 130, andhere, the value is Zo.

The load switching unit 130 is a functional unit that performs switchingbetween a matching resistance 132 whose resistance value isapproximately equal to Zo, a load control unit 133, and an intermediateresistance 131. The intermediate resistance 131 has a resistance valuethat is lower than the high resistance 127 and higher than the matchingresistance 132. The intermediate resistance 131 is for setting theimpedance of the power receiving antenna 125 seen by the powertransmitting antenna 115 to an intermediate impedance (referred to as“Md-Z” below) by connecting to the load switching unit 130. When theimpedance of the power receiving antenna 125 seen by the powertransmitting antenna 115 is set to Md-Z, a microcurrent flows in thepower receiving antenna 125 and the intermediate resistance 131.

The load control unit 133 is an impedance conversion circuit thatperforms an operation of matching the load impedance that changesaccording to the power consumption of the load 118 with thecharacteristic impedance 119 (Zo), and it is constituted by a DC-DCconverter or the like. Note that the load impedance means the impedancewhen the load 118 is seen by the load control unit 133.

Note that the impedance conversion operation is expressed as “loadimpedance control” in the description below. The load control unit 133and the matching resistance 132 have the same function in that they bothare both used to perform impedance matching with the resonance unit 128.However, after detecting a change in the impedance of the load 118, theload control unit 133 performs impedance conversion, and therefore acertain amount of time is required for the operation to stabilize. Onthe other hand, since the matching resistance 132 is a constantresistance, no time is required for the operation to stabilize.

Impedance in States of Periphery of Power Transmitting Range

FIGS. 2A to 2D are diagrams showing examples of states in the peripheryof the power transmission range in the power transmission system. Notethat a communication range 200 indicates a range in which communicationby means of the communication unit 116 in the power transmittingapparatus 100 is possible. A power transmission range 201 indicates arange in which power transmission by means of the power transmittingantenna 115 is possible. As shown in FIG. 2A, the communication range200 is configured to be larger than the power transmission range 201,and the communication range 200 is configured to contain the entirety ofthe power transmission range 201.

FIG. 2A shows a state where nothing is arranged in the powertransmission range 201. That is to say, the power receiving apparatus101 and a foreign substance 202 are not present in the powertransmission range 201. FIG. 2B shows a state where only the foreignsubstance 202 is present in the power transmission range 201. FIG. 2Cshows a state where only the power receiving apparatus 101 is present inthe power transmission range 201. Note that in FIG. 2C, the powertransmitting apparatus 100 is not transmitting power to the powerreceiving apparatus 101. FIG. 2D is the same as FIG. 2C in that thepower receiving apparatus 101 is present in the power transmission range201, but the power transmitting apparatus 100 is transmitting power tothe power receiving apparatus 101. Note that the arrow 202 conceptuallyillustrates that power is being transmitted.

If the object that is present in the power transmission range 201 is theforeign substance 202 (FIG. 2B), the power transmitting apparatus 100needs to perform control so as to not perform power transmission. On theother hand, if the object that is present in the power transmissionrange 201 is the power receiving apparatus 101 (FIG. 2C), the powertransmitting apparatus 100 needs to perform control so as to performpower transmission.

FIG. 3 is a diagram for describing an operation of the detection unit103. FIG. 3 includes the power transmitting antenna 115, the powerreceiving antenna 125, and the foreign substance 202. A voltage V1indicates a voltage at both terminals of the power transmitting antenna115. A current I1 indicates a current flowing in the power receivingantenna 125, and a current I2 indicates a current flowing in the foreignsubstance 202. Z is the impedance value of the power receiving antenna125.

The value of the voltage V1 changes according to the current I1 and thecurrent I2. Accordingly, the voltage V1 in the state where the foreignsubstance 202 and the power receiving apparatus 101 are not present inthe power transmission range 201 as shown in FIG. 2A (referred to hereas “V_init”) indicates a value that is different from the voltage V1 inthe state where the foreign substance 202 is present in the powertransmission range 201 as shown in FIG. 2B. In other words, if thevoltage V_init in the state where the foreign substance 202 and thepower receiving apparatus 101 are not present in the power transmissionrange 201 is stored in advance, the power transmitting apparatus 100 candetect the foreign substance 202 by detecting the voltage V1 in thestate in FIG. 2B and comparing it with V_init. Also, if the powerreceiving apparatus 101 is present in the power transmission range 201as shown in FIG. 2C, the voltage V1 similarly indicates a value that isdifferent from V_init. In other words, the power transmitting apparatus100 can detect that the foreign substance 202 or the power receivingapparatus 101 is present in the power transmission range 201 bycomparing the voltage V1 with V_init.

Incidentally, the magnitude of the current I1 that flows in the powerreceiving antenna 125 can be controlled by changing the impedance Z. Ifthe impedance Z is set to Hi-Z (e.g., infinity), the current I1 will bezero. If the power receiving apparatus 101 is present in the powertransmission range 201 as shown in FIG. 2C, the voltage V1 indicates avalue that is different from V_init, as described above. If the powerreceiving apparatus 101 performs control such that the impedance Z isset to Hi-Z, or in other words, such that the current I1 is set to zeroin this state, the voltage V1 will be equal to V_init.

In the state shown in FIG. 2C, the power transmitting apparatus 100 candetect that the foreign substance 202 or the power receiving apparatus101 is present in the power transmission range 201 based on the changein the voltage V1. However, the power transmitting apparatus 100 cannotdetermine whether the cause of the change is the foreign substance 202or the power receiving apparatus 101.

Incidentally, if the power receiving apparatus 101 controls theimpedance Z such that it is Hi-Z in the state shown in FIG. 2C, thecurrent I1 will be zero, and the voltage V1 will be V_init. In otherwords, the power transmitting apparatus 100 can determine that the powerreceiving apparatus 101 is present in the power transmission range 201.On the other hand, if the power receiving apparatus 101 controls theimpedance Z such that it is Hi-Z and the voltage V1 is not equal toV_init, the power transmitting apparatus 100 can detect that the foreignsubstance 202 is present in the power transmission range 201.

Also, if the power receiving apparatus 101 controls the impedance Z suchthat it is Md-Z in the state shown in FIG. 2C, a microcurrent will flowin the power receiving antenna 125 and the impedance Z. For this reason,the power receiving apparatus 101 can detect the power transmittingapparatus 100 by detecting the microcurrent. Note that the change in thevoltage V1 can also be expressed as a change in the input impedance ofthe power transmitting antenna 115 that is obtained by dividing thevoltage V1 by the current flowing in the power transmitting antenna 115.

FIG. 4 is a diagram showing an example of the configuration of theclass-E amplifier that constitutes the power transmission unit 113. Theclass-E amplifier is constituted by an N-channel MOSFET 405, twoinductors, and two capacitors. Reference numeral 403 indicates a gateterminal, reference numeral 402 indicates a drain terminal, andreference numeral 404 indicates a source terminal. Reference numeral 401indicates a DC voltage source that is input to the N-channel MOSFET 405.The power transmission unit 113 is connected to the power transmittingantenna 115 via the resonance control unit 114. For this reason, theinput impedance of the power transmitting antenna 115 is expressed as achange in the output impedance of the class-E amplifier. Also, a changein the output impedance of the class-E amplifier is expressed as achange in the output impedance of the DC voltage source 401.

In other words, if the output impedance value of the DC voltage sourcein the state shown in FIG. 2A is stored in advance, the powertransmitting apparatus 100 can detect the foreign substance 202 or thepower receiving apparatus 101. The output impedance value of the DCvoltage source in the state shown in FIG. 2A (initial impedance value)will be expressed as “Z_init” below.

Three impedance values (Hi-Z, Md-Z, and Zo) that are set as theimpedance of the power receiving apparatus 101 will be described next.

Hi-Z is an impedance value that is used for apparatus protection andapparatus detection. When a large current unexpectedly flows in thepower reception unit 117 including the power receiving antenna 125,there is a risk that the circuit will be damaged and it is verydangerous in terms of circuit protection. In view of this, the currentI1 that flows in the power reception unit 117 can be set to zero inprinciple by setting the impedance of the power receiving apparatus 101to Hi-Z, and the risk can be reduced. Accordingly, the power receivingapparatus 101 is set to Hi-Z as often as possible in the interest ofcircuit protection. Also, although the power transmitting apparatus 100can detect that at least one of the foreign substance 202 and the powerreceiving apparatus 101 is present in the power transmission range 201by detecting the change in the voltage V1 as described above, the powertransmitting apparatus 100 cannot identify which one it is. At thistime, if the impedance of the power receiving apparatus 101 is set toHi-Z, the power transmitting apparatus 100 can perform thisidentification.

Md-Z is the impedance value that is used for apparatus detection. Asdescribed above, the power receiving apparatus 101 can detect the powertransmitting apparatus 100 by setting the impedance to Md-Z. Also, sincethe voltage V1 of the power transmitting antenna 115 changes due to themicrocurrent that flows in the power receiving antenna 125, the powertransmitting apparatus 100 can detect the power receiving apparatus 101as well if the impedance of the power receiving apparatus 101 is set toMd-Z.

Zo is the impedance value that is used when the transmission efficiencyis to be calculated. If the output impedance of the power transmittingantenna (output impedance Z in FIG. 3 ) and the impedance of the loadhave not been matched, the transmission efficiency between the powertransmitting antenna 115 and the power receiving antenna 125 willdecrease due to reflection. For this reason, it is better not to performpower transmission in the case where, before starting power transmissionto the power receiving apparatus 101, the power transmitting apparatus100 calculates the transmission efficiency between the powertransmitting and receiving antennas and the efficiency is excessivelylow. In the case of using Hi-Z or Md-Z when calculating the transmissionefficiency, the transmission efficiency between the power transmissionand reception antennas cannot be calculated accurately since impedancematching between the power receiving antenna and the load cannot beachieved and there is a lot of reflection. Accordingly, when thetransmission efficiency is to be calculated, the impedance of the powerreceiving apparatus 101 is set to Zo such that matching can be achievedwith the output impedance Zo of the power receiving antenna. Needless tosay, in order to improve the transmission efficiency, the impedance ofthe power receiving apparatus 101 is set to Zo also when power is to bereceived from the power transmitting apparatus 100.

Operation of Detection Unit of Power Transmitting Apparatus

FIG. 5 is a timing diagram for describing operations of the powertransmission unit 113 and the detection unit 103. The horizontal axisindicates time. From time T1 to time T2, a detection signal 502 for thedetection unit 103 to perform Z-detection is transmitted by the powertransmission unit 113 via the power transmitting antenna 115. Also, fromtime T2 to time T3, a BT address that is an address uniquely assigned tothe communication unit 116 is transmitted using a BT address signal 503via the power transmitting antenna 115.

The detection unit 103 detects the impedance of the DC voltage source401 from time T1 to time T3. Square 504 indicates that the detectionunit 103 is performing Z-detection. Also, the height of square 504conceptually illustrates the magnitude of the impedance detected duringZ-detection. For example, in the case of FIG. 2A, the height of square504 corresponds to Z_init. Reference numeral 506, which includes thedetection signal 502 and the BT address signal 503, is referred to as a“pulse” in the description below.

Information Stored in Various Storage Units

FIG. 7 is a diagram showing an example of flags stored in the systemstate storage unit 105.

A power transmission flag 700 is a flag that is set to “1” when thepower transmitting apparatus 100 starts power transmission and is set to“0” when power transmission is stopped. A suspend flag 701 is a flagthat is set to “1” when power transmission is stopped while the controlunit 104 is performing the identification and is set to “0” at othertimes. A prohibit flag 703 is a flag that is set to “1” when powertransmission is prohibited, and is set to “0” at other times. Anapparatus flag 704 is a flag that is set to “1” if a BT connection hasbeen achieved between the communication unit 116 of the powertransmitting apparatus 100 and the communication unit 119 of the powerreceiving apparatus 101, and is set to “0” if not.

FIG. 8 is a diagram showing an example of information stored in the IDstorage unit 106 in the power transmitting apparatus. After the controlunit 104 has determined that the power receiving apparatus 101 is thecause of the impedance change, the BT address of the power receivingapparatus 101 is stored in a storage region 800. Also, if the controlunit 104 disconnects the BT connection with the power receivingapparatus 101, the BT address of the corresponding power receivingapparatus 101 is cleared from the storage region 800.

FIG. 9 is a diagram showing an example of information stored in the IDstorage unit 121 in the power receiving apparatus. When the pulse 506that is transmitted by the power transmission unit 113 via the powertransmitting antenna 115 is received by the power receiving antenna 125and the BT address included in the pulse 506 is detected, the detectedBT address is stored in the storage region 900. Also, when the powertransmitting apparatus 100 has stopped power transmission, or in otherwords, in the case where the suspend flag or the prohibit flag is “1”,the power receiving apparatus 101 deletes the BT address stored in thestorage region 900.

On the other hand, the BT address stored in the storage region 901 is aBT address for the power transmitting apparatus 100 that is received bythe communication unit 119 of the power receiving apparatus 101 via thecommunication unit 116 of the power transmitting apparatus 100. Thepower transmitting apparatus 100 transmits a later-described Inquirymessage, and when the power receiving apparatus 101 receives the Inquirymessage, the power receiving apparatus 101 detects the BT address of thepower transmitting apparatus that is the transmission source based onthe header information of the Inquiry message. Then, the detected BTaddress is stored in the storage region 901. Also, if the BT connectionbetween the power transmitting apparatus 100 and the power receivingapparatus 101 is disconnected, the power receiving apparatus 101 deletesthe BT address stored in the storage region 901.

FIG. 15 is a diagram showing an example of information stored in theimpedance storage unit 110. The impedance value obtained as a result ofthe Z-detection performed by the detection unit 103 is stored(overwritten) in Z_now in column 1501. Note that the detection unit 103copies the content of Z_now to Z_before in column 1500 before thecontent is overwritten. By doing so, the impedance value in the previousZ-detection is stored in Z_before, and it is possible to compareZ_before with Z_now, which is the result of the most recent Z-detection.

Power Transmission System Operation Example 1 (Operation when ForeignSubstance is Present)

FIGS. 6A and 6B are timing diagrams for describing operations of thepower transmitting apparatus. In particular, FIG. 6A is a timing diagramfor the power transmitting apparatus 100 in the case where the foreignsubstance 202 enters the power transmission range 201 at time Ta4, andthe horizontal axis indicates time. Also, FIGS. 10A and 10B are aflowchart of operations for the detection unit 103.

Operations of the power transmitting apparatus 100 in the state shown inFIG. 2A, or in other words, in the initial state where nothing isarranged will be described first. In the state shown in FIG. 2A, thesystem state storage unit 105 is in a state where the flags shown in row705 have been stored. According to row 705, the power transmittingapparatus 100 is not transmitting power, and the power transmission flag700 is “0” (NO in step S1000).

Accordingly, the detection unit 103 updates Z_before to Z_init. Then,the first timer 107 is reset at time Ta1 (step S1002). When the firsttimer 107 times out at time Ta2 (YES in step S1003), the detection unit103 transmits the pulse 506 in the period up to time Ta3 (step S1004).Then, the detection unit 103 performs Z-detection from Ta2 to Ta3 (stepS1005).

Square 602 shows that the detection unit 103 performs Z-detection fromtime Ta2 to time Ta3, and the height of square 602 conceptuallyillustrates the magnitude of the impedance detected at that time.According to FIG. 6A, the height of square 602 is equal to Z_init.Accordingly, the detection unit 103 stores Z_init in Z_now (step S1006).

Row 1502 shows the information stored in the impedance storage unit 110at this time. In row 1502, Z_before and Z_now are both equal to Z_init(YES in step S1011). Also, according to row 705, the power transmissionflag 700 is “0” (NO in step S1012), the prohibit flag 703 is “0” (NO instep S1013), and the apparatus flag 704 is also “0” (NO in step S1016).Accordingly, the detection unit 103 once again resets the first timer107 at time Ta3.

Next, it is presumed that the foreign substance 202 has entered thepower transmission range 201 at time Ta4. That is to say, it is presumedthat the state shown in FIG. 2B is entered at time Ta4. Square 604 showsthat the foreign substance 202 is present in the power transmissionrange 201 from time Ta4 to time Ta7.

The detection unit 103 performs Z-detection from Ta5 to Ta6. Note thatthe Z-detection is set to time out at T6 using the first timer 107. Theimpedance detected at this time is indicated by square 603. The heightof square 603 conceptually illustrates the magnitude of the impedancedetected at this time, and here it is Z1. According to FIG. 6A, theheight Z1 of the square 602 is not equal to Z_init.

Row 1503 shows the information stored in the impedance storage unit 110at this time. In row 1503, Z_now and Z_before are not equal (NO in stepS1011). Accordingly, the detection unit 103 determines that the foreignsubstance 202 or the power receiving apparatus 101 is present in thepower transmission range 201 (step S1018).

The flags stored in the system state storage unit 105 at this time areas shown in row 705, and the power transmission flag 700 is “0” (NO instep S1019). Next, the detection unit 103 updates the suspend flag 701to “1” (step S1020). The system state storage unit 105 at this time isas shown in row 706. According to row 706, the suspend flag 701 is “1”,which means that the control unit 104 needs to identify which of theforeign substance 202 and the power receiving apparatus 101 is the causeof the impedance change. In order to perform the identification, thedetection unit 103 starts the control unit 104 and the procedure movesto step S1100 (FIG. 11A).

FIGS. 11A and 11B are a flowchart of operations for BT control in thepower transmitting apparatus 100. The state here is the state shown inFIG. 2B, and the power receiving apparatus 101 is not present. For thisreason, the BT (communication unit 116) of the power transmittingapparatus 100 has not been started (NO in step S1100). Accordingly, thecontrol unit 104 starts the BT as the master (step S1101) and transmitsan Inquiry message for performing inquiry of peripheral BT-compatibledevices with the BT standard from the communication unit 116 (stepS1102, 605).

Here, if the power receiving apparatus 101 is present, an Inquiryresponse message (response signal) that is a response to the Inquirymessage is sent as a response. However, the foreign substance 202 doesnot respond to the Inquiry message, and therefore the control unit 104does not receive the Inquiry response message (NO in step S1103).Accordingly, the control unit 104 determines that the cause of theimpedance change detected from time Ta5 to Ta6 is not compatible with BT(step S1127), and determines that it is the foreign substance 202 (stepS1120). Additionally, the suspend flag 701 is updated to “0” (stepS1121) and the prohibit flag 703 is updated to “1” (step S1122).

Then, the control unit 104 performs error display on the display unit112 so as to notify the user that the foreign substance 202 is presentin the power transmission range 201, or that power transmission isprohibited (step S1123). The flags stored in the system state storageunit 105 at this time are as shown in row 707. The prohibit flag 703 is“1” since the foreign substance 202 is present in the power transmissionrange 201. According to row 707, the power receiving apparatus 101 isnot connected by BT and the apparatus flag 704 is “0” (NO in stepS1124). For this reason, the control unit 104 causes the detection unit103 to operate in order to check that the foreign substance 202 has beenremoved from the power transmission range 201 (step S1126), and theprocessing returns to step S1000 (step S1129). Here, at Ta7, it ispresumed that after viewing the error display, the user removes theforeign substance 202 from the power transmission range 201 for example.

From time Ta8 to time Ta9, the detection unit 103 transmits the pulseand performs Z-detection. Since the foreign substance 202 has beenremoved from the power transmission range 201, the state from Ta8 to Ta9is the state shown in FIG. 2A, and the impedance storage unit 110 is asshown in row 1502. According to row 707, the prohibit flag 703 is “1”(YES in step S1013), and therefore the detection unit 103 determinesthat the foreign substance 202 has been removed (step S1017), theprohibit flag 703 is updated to “0”, and thereafter the error display isswitched off (step S1015). Then, the detection unit 103 returns to theprocessing of step S1000.

As described above, the output impedance of the DC voltage source forthe class-E amplifier when a pulse is transmitted in the state where theforeign substance 202 and the power receiving apparatus are not presentin the power transmission range 201 is stored by the detection unit 103as Z_init. Also, the configuration is such that a pulse is periodicallytransmitted via a power transmitting antenna and the output impedance atthat time is compared with the stored Z_init. Accordingly, by detectingthe impedance change, the power transmitting apparatus 100 can recognizethat at least one of the foreign substance 202 and the power receivingapparatus 101 is present in the power transmission range 201.Additionally, by recognizing that there is no response for an Inquirymessage, the power transmitting apparatus 100 can recognize that theforeign substance 202 is present.

Note that in the description above, the detection unit 103 is configuredto detect the output impedance of the DC voltage source 401, but it maybe configured so as to detect another physical amount that changes dueto the foreign substance 202 being electromagnetically coupled with thepower transmitting antenna 115. For example, a configuration is possiblewhere the voltage V1 of the power transmitting antenna 115 is detected.Also, the power transmitting apparatus 100 causes the communication unit116 to operate as the BT master and transmits the Inquiry messagedenoted by 605. Therefore, a foreign substance that does not respond toan Inquiry message can be promptly identified. The inquiry message maybe another packet for which a response from the power receivingapparatus 101 is expected. Also, the communication unit 116 may beconfigured to use a communication standard other than BT (e.g., wirelessLAN).

Power Transmission System Operation Example 2 (Operation when PowerReceiving Apparatus is Present)

FIG. 6B is a timing diagram for the power transmitting apparatus 100 andthe power receiving apparatus 101 in the case where the power receivingapparatus 101 is present in the power transmission range 201. Note thatthe horizontal axis indicates time, and the vertical axis conceptuallyillustrates the impedance of the power receiving apparatus 101 seen bythe power transmitting antenna 115.

Also, Hi-Z, Md-Z, and Zo (Hi-Z>Md-Z>Zo) are indicated as threepredetermined impedance values. The control performed by the powerreceiving apparatus 101 for setting the impedance to the respectivevalues is as described above. Square 610 indicates that the impedance ofthe power receiving apparatus 101 is Hi-Z from time Tb1 to Tb2. Square611 indicates that the impedance of the power receiving apparatus 101 isMd-Z from time Tb2 to Tb3. Square 615 indicates that the impedance ofthe power receiving apparatus 101 is Zo from time Tb5 to Tb6.

Also, square 612 shows that the detection unit 103 transmits the pulse506 and performs Z-detection from time Tb2 to Tb3 and that theZ-detection result is indicated by a dashed line 624. As is evident fromcomparing the dashed line 624 and Z_init, the impedance detected by thedetection unit 103 from time Tb2 to time Tb3 is not equal to Z_init.

FIGS. 13A and 13B are a flowchart showing operations for BT control inthe power receiving apparatus 101. If the remaining battery power isless than or equal to a pre-determined threshold value (e.g., 95%) (YESin step S1300), the power receiving apparatus 101 starts the fourthtimer 122 at time Tb1 (step S1302) and the impedance of the powerreceiving apparatus 101 is set to Hi-Z (step S1303).

When the fourth timer 122 times out at time Tb2 (step S1304), the powerreceiving apparatus 101 starts the fifth timer 123 (step S1305) andconnects the switching unit 126 to the resonance unit 128 (step S1306).Then, the power receiving apparatus 101 connects the load switching unit130 to the intermediate resistance 131 and the impedance of the powerreceiving apparatus 101 is set to Md-Z (step S1307).

The functions of the fourth timer 122 and the fifth timer 123 will bedescribed here. The fourth timer 122 defines the amount of time that theimpedance of the power receiving apparatus 101 is set to Hi-Z, and thefifth timer 123 defines the amount of time that it is set to Md-Z. Inother words, if the power receiving apparatus 101 does not receive thepulse 506 from the power transmitting apparatus 100 (NO inlater-described step S1308), the power receiving apparatus 101 changesthe state to Hi-Z and Md-Z repeatedly.

The detection unit 103 detects an impedance that is different fromZ_init from time Tb2 to Tb3. Because of this, the detection unit 103recognizes that the foreign substance 202 or the power receivingapparatus 101 is present in the power transmission range 201.

Here, since the power receiving apparatus 101 has set the impedance toMd-Z, a microcurrent flows in the intermediate resistance 131 due to thepulse 506 (i.e., the detection signal 502 and the BT address signal 503)transmitted by the power transmission unit 113 from Tb2 to Tb3. In viewof this, the power receiving apparatus 101 can acquire the BT address ofthe power transmitting apparatus 100 that is included in the BT addresssignal 503 by detecting the voltage generated at both terminals of theintermediate resistance 131. At this time, the power receiving apparatus101 can recognize its own presence in the power transmission range 201of the power transmitting apparatus 100.

If the power receiving apparatus 101 receives the pulse 506 (controlsignal) (YES in step S1308), the impedance of the power receivingapparatus 101 is immediately set to Hi-Z at time Tb3 (step S1310),regardless of whether or not the fifth timer 123 has timed out, in theinterest of the aforementioned circuit protection.

Then, the power receiving apparatus 101 stores (updates) the BT addressof the power transmitting apparatus 100 acquired in step S1311 in thestorage region 900 of the ID storage unit 121 (step S1312). Here, the BTaddress (identifier) of the power transmitting apparatus 100 that wasacquired from the pulse 506 is “aa aa aa aa aa aa”. Then, the powerreceiving apparatus 101 starts the BT (communication unit 119) (stepS1313).

Meanwhile, upon detecting that the impedance has changed around timeTb3, the power transmitting apparatus 100 starts the BT (communicationunit 116) (step S1101) and transmits the Inquiry message (step S1102,605).

Upon receiving the Inquiry message (YES in step S1314), the powerreceiving apparatus 101 acquires the BT address of the transmissionsource device stored in the header portion of the Inquiry message andstores (updates) it in the storage region 901 of the ID storage unit121. Then, the power receiving apparatus 101 compares the two BTaddresses stored in the storage regions 900 and 901 of the ID storageunit 121 (step S1316).

FIG. 9 shows the two BT addresses stored in the ID storage unit 121 atthis time. According to FIG. 9 , the BT address in the storage region900 and the BT address in the storage region 901 both match the BTaddress of the power transmitting apparatus 100 (YES in step S1317). Inview of this, in step S1318, the power receiving apparatus 101determines whether or not connection to the device corresponding to theBT address stored in the ID storage unit 121 is complete. Here, BTconnection has not yet been performed (NO in step S1318). For thisreason, the power receiving apparatus 101 transmits the Inquiry responsemessage (response signal) (step S1319, 613) in response to the Inquirymessage transmitted by the device corresponding to a BT address storedin the ID storage unit 121 (in this case, the power transmittingapparatus 100) (response signal transmission means). In other words, thepower receiving apparatus recognizes its own presence in the powertransmission range 201 and subsequently transmits an Inquiry responsemessage (response signal).

Upon receiving the Inquiry response message denoted by 613 (YES in stepS1103), the power transmitting apparatus 100 determines whether or notthe transmission source of the Inquiry response message is a device thathas not been connected by BT. Here, since the power transmittingapparatus 100 and the power receiving apparatus 101 have not beenconnected by BT (YES in step S1104), the power transmitting apparatus100 performs authentication processing for the power receiving apparatus101.

Incidentally, a PIN code is used in BT authentication, andauthentication is successful if the PIN code used by the power receivingapparatus 101 is the same as that in the power transmitting apparatus100. In view of this, the power transmitting apparatus 100 uses its ownBT address as the PIN code for example (step S1105). Also, the powerreceiving apparatus 101 uses the BT address of the power transmittingapparatus 100 that was acquired from the pulse 506 in step S1311 as thePIN code (step S1320). Because the PIN codes have been made common tothe power transmitting apparatus 100 and the power receiving apparatus101, authentication is successful, and the same encryption key can beshared.

The power transmitting apparatus 100 generates an initialization keybased on the BT authentication procedure (step S1106) and transmits arandom number generated in the power transmitting apparatus 100 to thepower receiving apparatus 101 (not shown). Upon receiving the randomnumber, the power receiving apparatus 101 generates an initializationkey based on the PIN code and the random number.

Next, the power transmitting apparatus 100 transmits the newly-generatedrandom number to the power receiving apparatus (step S1107). Uponreceiving the random number in step S1107, the power receiving apparatus101 generates an SRES (Signal Response) message based on the randomnumber, the BT address of the power transmitting apparatus 100, and theinitialization key and transmits the SRES message to the powertransmitting apparatus 100.

Upon receiving the SRES message (step S1108), the power transmittingapparatus 100 compares the SRES message with its own generated SRESmessage (step S1109). As described above, the PIN code is used in commonby the power transmitting apparatus 100 and the power receivingapparatus 101, and therefore the SRES messages match (YES in stepS1109), and the authentication is successful (step S1110, YES in stepS1321).

Next, the power receiving apparatus 101 transmits an SDP (ServiceDiscovery Protocol) inquires message (step S1322). Upon receiving theSDP inquires message (step S1112), the power transmitting apparatus 100transmits an SDP response message including “Wireless Charger”, which isinformation regarding a service that can be provided (step S1113). Uponreceiving the SDP response message (step S1323), the power receivingapparatus 101 checks whether or not the desired service and the serviceacquired in step S1323 match (step S1324). Here, the power receivingapparatus 101 has requested the “Wireless Charger” service for chargingthe battery, which is the load 118, and therefore it is determined thatthe services match (YES in step S1325).

Since the BT connection with the power receiving apparatus 101 wassuccessful, the control unit 104 updates the apparatus flag 704 to “1”(step S1116). Then, the control unit 104 instructs the power receivingapparatus 101 to set the impedance to Hi-Z in order to determine whetheror not the foreign substance 202 is present in the power transmissionrange 201 (step S1117). Next, the control unit 104 causes the detectionunit 103 to operate, performs the processing of the above-describedsteps S1001, S1004, S1005, S1030, and S1006, and compares the resultwith the content of the impedance storage unit 110 (step S1118).

Here, it is presumed that from time Tb4 to Tb5, the power transmissionunit 113 has transmitted the pulse 506 transmitted in step S1004. Here,the state is that shown in FIG. 2C, and the foreign substance 202 is notpresent in the power transmission range 201. For this reason, theimpedance detected by the detection unit 103 from time Ta4 to time Ta5is equal to Z_init (YES in step S1119). For this reason, the controlunit 104 determines that the power receiving apparatus 101 is the causeof the impedance change detected from time Tb2 to time Tb3 (step S1114)and updates the BT address in the storage region 800 of the ID storageunit 106 to the BT address of the power receiving apparatus 101 (stepS1115). Note that the BT address of the power receiving apparatus 101can be acquired from the header or the like of the SDP response messagereceived in step S1112. Here, the BT address (identifier) of the powerreceiving apparatus 101 is “bb bb bb bb bb bb”.

FIGS. 12A and 12B are a flowchart of operations for power transmissioncontrol in the power transmitting apparatus 100. FIGS. 14A and 14B are aflowchart of operations for power reception control in the powerreceiving apparatus 101.

First, at time Tb4, the control unit 104 transmits an instruction tochange the impedance to Zo (Zo instruction) to the power receivingapparatus 101 in order to calculate the transmission efficiency betweenthe power transmitting antenna 115 and the power receiving antenna 125(step S1200, 614). Upon receiving the Zo instruction (YES in stepS1400), the power receiving apparatus 101 sets the impedance of thepower receiving apparatus 101 to Zo (step S1401) and transmits a Zoinstruction response indicating that the impedance has been set to Zo tothe power transmitting apparatus 100 (step S1402).

Upon receiving the Zo instruction response (step S1201), the controlunit 104 transmits the pulse 506 from the power transmitting antenna 115(step S1202). Upon receiving the pulse (YES in step S1403), the powerreceiving apparatus 101 transmits a power reception response indicatinga voltage value or a power value to the power transmitting apparatus 100(step S1431).

If the power reception response received in step S1203 is not zero (NOin step S1230), the control unit 104 derives the transmission efficiency(step S1204), causes the resonance control unit 114 to operate (stepS1205), and controls the resonance control unit 114 such that thetransmission efficiency peaks. If the transmission efficiency peaks (YESin step S1205), the transmission efficiency and the threshold value thatwas stored in advance are compared (step S1207). If the transmissionefficiency is greater than or equal to the threshold value (YES in stepS1208), the control unit 104 transmits an efficiency notification(efficiency is high) to the power receiving apparatus 101 (step S1231)and transmits the Hi-Z instruction (step S1232, 616). In this case, thepulse transmission for the efficiency calculation (step S1202) is notperformed thereafter. Upon receiving the efficiency notification (YES instep S1405), the power receiving apparatus 101 sets the impedance toHi-Z (step S1432), and transmits a Hi-Z instruction response indicatingthat the Hi-Z instruction was received and the impedance was set to Hi-Zto the power transmitting apparatus 100. Note that if the efficiency isless than the threshold value (NO in step S1208), it is sufficient thatcontrol is performed such that an efficiency notification (efficiency islow) is transmitted (step S1220) and power transmission is notperformed.

Next, the control unit 104 makes a request to the power receivingapparatus 101 to receive power reception parameters that indicate thepower amount requested by the power receiving apparatus 101, the peakvoltage allowable by the power reception unit 117, and the like (stepS1209), and the power receiving apparatus 101 responds to the request(step S1408). The control unit 104 compares the power receptionparameters acquired in step S1210 and its own power transmissioncapability and determines whether or not power transmission is possible(step S1211). Then, if power transmission is possible (YES in stepS1212), the control unit 104 causes the detection unit 103 to operate,performs the processing of the above-described steps S1001, S1004,S1005, S1030, S1006, and S1011, and compares the result with the contentof the impedance storage unit 110 (step S1233).

Here, it is presumed that from time Tb6 to Tb7, the power transmissionunit 113 has transmitted the pulse 506 transmitted in step S1004. Sincethe foreign substance 202 is not present in the power transmission range201 in the state shown in FIG. 2C, the impedance detected by thedetection unit 103 from time Ta6 to time Ta1 is equal to Z_init (YES instep S1234). Because of this, the control unit 104 transmits a powertransmission permitted notification to the power receiving apparatus 101(step S1213), and upon receiving a power transmission permitted response(step S1214), the control unit 104 instructs the power receivingapparatus 101 to connect to the charge circuit (step S1215).

Note that the detection unit 103 is operated from time Ta6 to Ta7because there is a possibility that the foreign substance 202 enters thepower transmission range 201 in the period from Tb5 to Tb6. In this way,before starting power transmission, the control unit 104 always causesthe detection unit 103 to operate and checks that there is no foreignsubstance 202.

Upon receiving the power transmission permitted notification (YES instep S1409), the power receiving apparatus 101 transmits the powertransmission permitted response (step S1410). Then, the power receivingapparatus 101 receives a charge circuit connection instruction (stepS1411) and connects the load switching unit 130 to the load control unit133 (step S1412). Furthermore, the power receiving apparatus 101 startsthe load control unit 133 (step S1413) and transmits a charge circuitconnection response (step S1414).

Upon receiving the charge circuit connection response (step S1216), thecontrol unit 104 performs notification of the start of powertransmission and starts power transmission at time Tb7 (step S1217,617). Then, the control unit 104 updates the suspend flag 701 to “0”(step S1218) and updates the power transmission flag 700 to “1” (stepS1219).

The power receiving apparatus 101 starts load impedance control (stepS1415), starts power reception upon receiving the power transmissionstart notification (step S1416), and displays the fact that charging isbeing performed on the display unit 124. At this time, the state is thatshown in FIG. 2D, and the system state storage unit 105 is in a statewhere the flags shown in row 708 have been stored.

From time Tb7 and onward, the impedance of the power receiving apparatus101 is constant at Zo. Since the power transmission unit 113 uses aclass-E amplifier, the impedance of the DC voltage source detected bythe detection unit 103 is constant as well. Here, Z_tx is the impedanceof the DC voltage source when the power transmitting apparatus 100 istransmitting power from Tb7 onward, and square 618 indicates Z_tx.

Upon starting power transmission (YES in step S1000), the powertransmitting apparatus 100 resets the second timer that times out in amicro-period (e.g., several milliseconds) that is shorter than that ofthe first timer. Then, when the second timer has timed out, the powertransmitting apparatus performs Z-detection.

Here, if the foreign substance 202 has entered the power transmissionrange 201 while power transmission is in progress, the result of theZ-detection will be a value that is different from Z_tx due to theinfluence of the foreign substance 202. At this time, the control unit104 recognizes that the foreign substance 202 or a new power receivingapparatus that is not shown in FIG. 2D has entered the powertransmission range 201, or that the power receiving apparatus 101 hasmoved outside of the power transmission range 201 and the impedance haschanged. The power transmitting apparatus 100 performs the followingprocessing and determines whether the cause of the impedance change isthe foreign substance 202, a new power receiving apparatus, or movementof the power receiving apparatus 101.

Since the power transmission flag is “1” (YES in step S1019), the powertransmitting apparatus 100 transmits a power transmission suspensionnotification to the power receiving apparatus 101 indicating that powertransmission is to be interrupted until the determination ends (stepS1025). Then, the power transmission flag is updated to “0” (step S1027)and power transmission stops (step S1026). Then, the power transmittingapparatus 100 transmits the Hi-Z instruction to the power receivingapparatus 101 (step S1028).

Upon receiving the power transmission suspension notification (YES instep S1429), the power receiving apparatus 100 transmits a powertransmission suspension notification response. At this time, the powerreceiving apparatus 101 recognizes that power transmission has beensuspended since the power transmitting apparatus 100 is to perform thedetermination, or that the power receiving apparatus 101 itself hasmoved outside of the power transmission range 201. Also, when powertransmission is stopped (step S1430), the power receiving apparatus 101no longer recognizes whether or not it is in the power transmissionrange 201, and therefore the BT address stored in the storage region 900is deleted (step S1422). Also, upon receiving the power transmissionsuspension notification, the power receiving apparatus 101 does notswitch off the charge display (step S1421), regardless of the fact thatpower transmission has been stopped. Then, when the Hi-Z instruction isreceived, the impedance is set to Hi-Z (step S1423) and the Hi-Zinstruction response is subsequently transmitted.

Upon receiving the Hi-Z instruction response (YES in step S1029), thepower transmitting apparatus 100 updates the suspend flag 701 to “1”(step S1020). Then, the power transmitting apparatus 100 returns to theprocessing of step S1100 in order to perform the identification (stepS1023). At this time, the system state storage unit 105 is in the statein which the flags shown in row 709 are stored.

Since the impedance of the power receiving apparatus 101 is Hi-Z at thistime, the Z-detection performed by the power transmitting apparatus 100is not influenced by the power transmitting apparatus. Accordingly, thepower transmitting apparatus 100 detects the foreign substance 202 usingthe processing that was described above with reference to FIG. 2A (stepS1120). Since the apparatus flag 704 is “1” (YES in step S1126), thepower transmitting apparatus 100 transmits an error notification to thepower receiving apparatus 101 (step S1126). The system state storageunit 105 at this time is in the state in which the flags shown in row710 are stored. Upon receiving the error notification (YES in stepS1424), the power receiving apparatus 101 switches off the chargedisplay (step S1425) and performs error display on the display unit 124(step S1426).

The power transmitting apparatus 100 causes the detection unit tooperate in step S1126 and moves to the processing of step S1000 (stepsS1126, S1129), and therefore, as described above with reference to FIG.2A, it is possible to detect that the foreign substance 202 has beenremoved.

When the foreign substance 202 has been removed, the apparatus flag 704is “1” (YES in step S1016), and therefore the power transmittingapparatus 100 transmits an error cancel notification to the powerreceiving apparatus (step S1021). Upon receiving the error notification(YES in step S1427), the power receiving apparatus 101 moves to stepS1400 and waits for the Zo instruction. Thereafter, the powertransmitting apparatus 100 starts power transmission using theprocessing that was described with reference to FIG. 6B.

Also, if a new power receiving apparatus has entered the powertransmission range 201 while power transmission is in progress, theZ-detection result will indicate a value that is different from Z_tx dueto the influence of the new power receiving apparatus. Because of this,the power transmitting apparatus 100 can detect the new power receivingapparatus using the processing that was described above with referenceto FIG. 2B. Then, in step S1200, a Zo instruction is given for all ofthe BT addresses stored in the storage region 800 at this time. In otherwords, the Zo instruction is given for the BT address of the powerreceiving apparatus 101 and the BT address of the new power receivingapparatus. Then, the power transmitting apparatus 100 startstransmitting power to the power receiving apparatus 101 and the newpower receiving apparatus. In step S1421, it is sufficient that thepower receiving apparatus 101 does not switch off the charge displaywhile the power transmitting apparatus 100 is performing thedetermination, or in other words, when there is a possibility of beingable to continue to receiving power regardless of the fact that powertransmission has been stopped. Accordingly, if new power receivingapparatuses frequently enter the power transmission range 201, thecharge display is not switched off each time, and the user of the powerreceiving apparatus 101 need not worry that charging is not beingperformed.

Note that if another BT device that can respond to the Inquiry messagebut does not have shared information is present in the powertransmission range 201 for example, a negative determination is made instep S1109, and the power transmitting apparatus 100 determines that theother BT device is a foreign substance (step S1120).

As described above, in the wireless power transmission system accordingto the first embodiment, the output impedance of the DC voltage source401 in the state where the foreign substance 202 and the power receivingapparatus 101 are not present in the power transmission range 201(initial state) is stored as Z_init by the detection unit 103. Then, byperiodically transmitting a pulse via the power transmitting antenna 115and comparing the output impedance at that time and Z_init, it ispossible to realize foreign substance detection without the addition ofa special circuit.

Also, the power receiving apparatus 101 has a function of controllingthe impedance. Due to the power receiving apparatus 101 controlling theimpedance in accordance with instructions from the power transmittingapparatus 100, the power transmitting apparatus 100 can identify whichof the foreign substance 202 and the power receiving apparatus 101 ispresent in the power transmission range 201. Also, the powertransmitting apparatus 100 can transmit power to the power receivingapparatus 101 with a more preferable transmission efficiency.

Also, if Z_init and Z_before are not equal in step S1234 (NO in stepS1234), the power transmitting apparatus determines that a foreignsubstance is present (steps S1235, S1120) and prohibits powertransmission. By doing so, power transmission can be prohibited when aforeign substance has entered the power transmission range in the periodfrom time Tb5 to Tb6.

Also, if the SRES messages do not match, the power transmittingapparatus determines that a foreign substance is present and prohibitspower transmission. This corresponds to the case where a BT device thatcannot receive the Wireless Charger service enters the powertransmission range and BT authentication processing is performed. Inthat case, the power transmitting apparatus can consider the BT deviceas being equal to a foreign substance and not perform power transmissionthereto.

Also, if the power receiving apparatus does not transmit an expectedresponse, communication by means of BT may be stopped. The case wherethe Zo instruction response is not received from the power receivingapparatus and the case where the power reception parameter response isnot received are examples of cases where an expected response is nottransmitted.

Also, another example of this is the case where the power transmittingapparatus is configured to transmit a power transmission abilitydetermination notification in step S1212 regardless of the determinationresult and the power receiving apparatus is configured to transmit apower transmission ability determination response in response to thenotification, but the power transmitting apparatus does not receive thepower transmission ability determination response. Alternatively, otherexamples of this are the case where the power transmitting apparatusdoes not receive the power transmission permitted response, and the casewhere the power transmitting apparatus does not receive the chargecircuit connection response.

Furthermore, other examples are the case where the power receivingapparatus is configured to transmit a power transmission startnotification response in response to a power transmission startnotification, but the power transmission start response is not received,or the Hi-Z instruction response is not received. Also, another exampleis the case where the power receiving apparatus is configured totransmit an error notification response in response to an errornotification, but the power transmitting apparatus does not receive theerror notification response. Also, another example is the case where thepower receiving apparatus is configured to transmit an error cancelnotification response in response to an error cancel notification, butthe power transmitting apparatus does not receive the error cancelnotification response. Also, another example is the case where the powerreceiving apparatus is configured to transmit an efficiency notificationresponse in response to an efficiency notification, but the efficiencynotification response is not received.

In the above cases, it is conceivable that the power receiving apparatushas been moved outside of the communication range for some reason, thatthe power receiving apparatus has malfunctioned, that the communicationunit of the power transmitting apparatus has malfunctioned, or the like.Also, the power transmitting apparatus may be configured to stop orprohibit power transmission also in the case where BT communication hasbeen disconnected due to deterioration in the communication environmentor the like. By doing so, power transmission can be stopped orprohibited in the case where control signals can no longer be exchanged.

Also, if the power transmitting apparatus does not execute the nextexpected processing, the power receiving apparatus may disconnect fromBT, delete the BT address from the storage region 901, and subsequentlystop BT. The case where the power receiving apparatus does not receivethe power transmission ability determination, the case where the Hi-Zinstruction is not received, the case where the power transmissionpermitted notification is not received, and the case where the chargecircuit connection instruction is not received are examples of caseswhere the power transmitting apparatus does not perform the expectedprocessing.

Also, another example is the case where the power receiving apparatus isconfigured to detect the power reception amount received from the powertransmitting apparatus, and the power transmission suspensionnotification is not received regardless of the fact that the powerreception amount is 0. Also, another example is the case where the powerreceiving apparatus does not receive the pulse in step S1403 (NO in stepS1403). Note that if the pulse is not received in step S1403 (NO in stepS1403), before disconnecting BT, the power receiving apparatus maytransmit a power reception inability notification to the powertransmitting apparatus indicating that the pulse was not received.

The case where the power receiving apparatus that is present in thepower transmission range is taken or moved outside of the powertransmission range and the case of malfunction in the power receivingapparatus or the power transmitting apparatus are examples that alsocorrespond to the above cases. Thus, it is possible to handle caseswhere unexpected circumstances arise in the power transmitting apparatusand the power receiving apparatus.

Also, due to the configuration where the second timer is set to amicro-period, the entry of the foreign substance 202 into the powertransmission range 201 can be immediately detected and powertransmission can be promptly stopped. Also, by setting the first timerto a longer time period than the second timer, it is possible to achievelow power consumption in the power transmitting apparatus in the statewhere power transmission is not being performed, or where the BT has notbeen started.

Also, if the Inquiry message response has been received, the powertransmitting apparatus checks whether or not the foreign substance ispresent in the power transmission range by setting the impedance of thepower receiving apparatus to Hi-Z. By doing so, the error notificationcan be transmitted to the power receiving apparatus and notification ofthe fact that power transmission is prohibited can be performed in thecase where the foreign substance is present.

Also, the power transmitting apparatus performs Z-detection before theefficiency calculation. By doing so, the foreign substance can bedetected before the efficiency calculation is performed, and theefficiency calculation can be performed with accuracy. Also, Z-detectionis performed before the start of power transmission, and therefore, if aforeign substance has entered the power transmission range in the periodfrom time Tb5 to Tb6, the power transmitting apparatus can recognize theentry of the foreign substance before the start of power transmission.

In addition, even when the power transmission suspension notification isreceived in step S1429 and power reception is interrupted, the powerreceiving apparatus does not switch off the charge display until theerror notification is received. By doing so, the charge display canremain on in the case where there is a possibility that power receptioncan continue, even if power reception has been interrupted. In otherwords, in the case where multiple power receiving apparatuses enter thepower transmission range 201 one after another, the charge display isnot switched off each time.

Also, upon recognizing its own presence in the power transmission range201, the power receiving apparatus performs BT authenticationprocessing. By doing so, after the BT authentication for the powerreceiving apparatus is successful, the power transmitting apparatus canrecognize that the power receiving apparatus is present in the powertransmission range 201. Also, since the power receiving apparatus firstrecognizes its own presence in the power transmission range and thentransmits the Inquiry response message, the power transmitting apparatuscan recognize that the power receiving apparatus that transmitted theInquiry response message is present in the power transmission range.Accordingly, the power transmitting apparatus can realize communicationcontrol with the power receiving apparatus that is present in the powertransmission range 201.

Also, the power transmitting apparatus performs notification of its ownBT address via the power transmitting antenna used in the powertransmission range 201 that is smaller than the communication range 200.Then, the power receiving apparatus performs authentication processingwith only the power transmitting apparatus having the BT address thatwas acquired using the power receiving antenna. By doing so, the powerreceiving apparatus can avoid the problem of connecting via BT toanother adjacent power transmitting apparatus.

Also, if the next expected instruction or notification is not receivedfrom the power transmitting apparatus, the power receiving apparatusstops the communication unit. By doing so, system malfunction can beprevented. Also, if an expected response is not received from the powerreceiving apparatus, the power transmitting apparatus also stops acommunication unit and stops the power transmission sequence. By doingso, system malfunction can be prevented.

Also, the power transmitting apparatus starts the communication unitafter detecting an impedance change. By doing so, power is not suppliedneedlessly to the communication unit and low power consumption can berealized.

Also, if the remaining battery power is greater than a threshold value(NO in step S1300, YES in step S1418), the power receiving apparatussets the impedance to Hi-Z (steps S1301, S1431). By doing so, a powerreceiving apparatus that does not need to be charged will not influencethe Z-detection executed by the power transmitting apparatus 100. Also,if the remaining battery power is greater than the threshold value (NOin step S1300, YES in step S1418), the power receiving apparatus doesnot connect to the power transmitting apparatus by BT, and it ispossible to achieve power conservation in the power receiving apparatusand the power transmitting apparatus.

Modified Example 1

Other configurations will be described below, and similar effects canalso be obtained with any of these configurations or a combinationthereof below.

The high resistance may be a capacitor indicating a high impedance inthe frequency of a high-frequency voltage generated in the powerreceiving antenna. It is also conceivable to not include the highresistance 127. In that case, the power receiving antenna is in an openstate, and there is no current flowing in the power receiving antenna.In other words, the impedance of the power receiving antenna can be setto an extremely high value. Also, Z_init need not be a fixed value andmay be a value obtained by giving a margin of error to a fixed value.For example, similar effects can also be obtained with a value of 100ohms±3%.

Also, the pulse was described as having a configuration where thedetection signal 502 and the BT address signal 503 are combined, but itis possible to use only the BT address signal 503. Also, the powertransmitting apparatus is configured to transmit the pulseintermittently, but similar effects can be obtained using aconfiguration of continuous transmission as well.

Also, after transmitting the error cancel notification (step S1021), thepower transmitting apparatus may transmit an Md-Z instruction forsetting the impedance to Md-Z to the power receiving apparatus, and thepower receiving apparatus may set the impedance to Md-Z. By doing so,the power receiving apparatus can recognize whether or not it is presentin the power transmission range 201, and therefore system malfunctioncan be prevented.

Also, in the description above, the power transmitting apparatusnotifies its own BT address to the power receiving apparatus via thepower transmitting antenna. It is also possible to perform notificationof a BT address on which a specific arithmetic operation has beencarried out. Due to the power transmitting apparatus and the powerreceiving apparatus sharing the specific arithmetic operation, a similareffect can be obtained and security is improved. Examples of thespecific arithmetic operation include a method of finding the exclusiveOR of a predetermined 6-byte bit string and the bit string of the BTaddress (6 bytes).

Additionally, it is also possible to transmit a pulse including theaddition of the PIN code, rather than a pulse including only the BTaddress. Using a configuration where the PIN code is changed asappropriate increases the complexity of the encryption key and increasessecurity.

Also, in the description above, the power transmitting apparatusnotifies its own BT address to the power receiving apparatus via thepower transmitting antenna. The BT address may be other information bywhich the power transmitting apparatus can be identified. For example,the BT address may be a random number generated randomly by the powertransmitting apparatus. In this case, the power transmitting apparatustransmits the random number from time Tb2 to Tb3 and attaches the randomnumber to the Inquiry message. Then, a similar effect can be obtainedalso when the power receiving apparatus compares the received randomnumber and the random number attached to the Inquiry from time Tb2 toTb3 in step S1316.

Also, in the BT authentication and encryption key generation processing,the power receiving apparatus may include an information elementindicating that it can receive the Wireless Charger service in theInquiry response message and transmit this Inquiry response message tothe power transmitting apparatus as a response. For example, the powerreceiving apparatus may include “Wireless Power Receiver” as theinformation element. By performing authentication processing with onlythe transmission source of the response including the informationelement among the received Inquiry responses, the power transmittingapparatus can avoid performing needless authentication processing with aBT device that cannot receive the Wireless Charger service.

Also, in the above description, the power transmitting apparatusoperates as the master device and the power receiving apparatusdetermines whether or not to transmit the Inquiry response based on theaddress of the Inquiry transmission source. However, another packet thatis exchanged before the encryption key is shared in step S1111, or inother words, another packet that is expected as a response from theslave device may be used. For example, an ID packet that is exchanged atthe time of calling (Page) may be used.

Also, the BT address signal 503 is configured to be transmitted by thepower transmitting apparatus, but a configuration is possible where thepower receiving apparatus transmits its own BT address. In this case,the power receiving apparatus controls the connection between an antennaswitching switch and the resonance unit for example, and therebymodulates the load according to the pulse transmitted by the powertransmitting apparatus. This changes the impedance when the powerreceiving apparatus is seen by the power transmitting apparatus andenables transmission of BT address information.

In this case, a configuration is used where the power transmittingapparatus has the storage region 900 and the storage region 901. Thepower transmitting apparatus stores the BT address of the powerreceiving apparatus that was received using load modulation in thestorage region 900, and stores the BT address of the power receivingapparatus that is the Inquiry response message transmission source inthe storage region 901. Then, the power transmitting apparatus comparesthe BT addresses using the processing in step S1316 and performsauthentication and encryption key generation processing on the BTaddresses if they match. In this case, BT authentication processing isperformed with only the power receiving apparatus that is present in thepower transmission range 201, and therefore the SRES messages alwaysmatch and needless authentication processing for other BT devices is notperformed.

Also, the power transmitting apparatus and the power receiving apparatusmay both transmit the corresponding BT addresses from the powertransmitting antenna and the power receiving antenna. In this case, aconfiguration is used where the power transmitting apparatus and thepower receiving apparatus both have the storage region 900 and thestorage region 901. Upon receiving the BT address 503 of the powertransmitting apparatus at time T3 in FIG. 5 , the power receivingapparatus subsequently transmits the BT address of the power receivingapparatus. In this case, the power receiving apparatus transmits theInquiry response to only the power transmitting apparatus that ispresent in the power transmission range 201. Also, since the powertransmitting apparatus performs authentication processing with only thepower receiving apparatus that is present in the power transmissionrange 201, there is an effect of not performing needless processing suchas performing authentication processing with a BT device that cannotreceive the Wireless Charger service.

Modified Example 2

In addition, similar effects can be obtained also in the case where thecommunication unit 116 and the communication unit 119 are compatiblewith a communication standard other than BT, such as wireless LAN. Inthe case of wireless LAN, it is sufficient to use a configuration wherethe BT address is replaced with a MAC address, the Inquiry message isreplaced with a ProbeRequest message, and the Inquiry response messageis replaced with a ProbeResponse message.

For example, in the authentication and connection processing, it ispossible to use a Wi-Fi Direct Service standard (referred to as WDFSstandard below), which the Wi-Fi alliance is considering standardizing.The WFDS standard is a protocol than can realize authentication andconnection processing between one access point and one station on awireless LAN. Also, the power transmitting apparatus and the powerreceiving apparatus are both configured to transmit the correspondingMAC addresses from the power transmitting antenna and the powerreceiving antenna.

Then, if the MAC addresses stored in the storage region 900 and thestorage region 901 match, the power transmitting apparatus and the powerreceiving apparatus start WFDS. Then, if authentication and connectionprocessing are performed only with a wireless LAN apparatus having theMAC address that is stored in the storage region 900 and the storageregion 901 by the power transmitting apparatus and the power receivingapparatus respectively, the power transmitting apparatus can performcommunication control with the power receiving apparatus that is presentin the range in which power transmission can be performed.

Here, a case will be considered where multiple power receivingapparatuses are present in the power transmission range 201 in thesystem in which control signals are exchanged using a wireless LAN. Itis presumed that a power receiving apparatus operating as an accesspoint has gone outside of the communication range 200 for some reason.Thus, the wireless LAN connection between the power transmittingapparatus and the power receiving apparatus operating as the accesspoint is disconnected. For this reason, the power transmitting apparatuscannot exchange control signals with the remaining power receivingapparatuses. Because of this, it is desirable that the powertransmitting apparatus is configured to operate as the access point.

Note that a wireless LAN terminal that is compatible with WFDS maypossibly be a station or an access point. In a GroupNegotiation phase(referred to below as a “GN phase”) in the WFDS standard, it isdetermined whether the wireless LAN terminal is to serve in the role ofthe station or the access point. Also, with the WFDS standard, thewireless LAN terminal having a larger intent value from 0 to 15 that isexchanged in the GN phase is to serve in the role of the access point,and the wireless LAN terminal have the smaller intent value is to servein the role of the station.

Because of this, it is sufficient that the intent value transmitted bythe power transmitting apparatus is made larger than the intent valuetransmitted by the power receiving apparatus. For example, by settingthe intent value transmitted by the power transmitting apparatus 100 tothe power receiving apparatus 101 in the GN phase to “15” and settingthe intent value transmitted by the power receiving apparatus 101 to thepower transmitting apparatus 100 in the GN phase to “0”, the powertransmitting apparatus 100 can operate as the access point, and thepower receiving apparatus 101 can operate as the station.

In addition, although the WFDS standard has been described as an exampleof a protocol for performing authentication and connection processing,it is also possible to use the Wi-Fi Direct standard.

Also, the power transmitting apparatus and the power receiving apparatusare both configured to transmit the corresponding MAC addresses from thepower transmitting antenna and the power receiving antenna, but aconfiguration is also possible where one of the power transmittingapparatus and the power receiving apparatus performs transmissionthereof. Thus, based on a wireless LAN standard, the power transmittingapparatus can perform communication control with the power receivingapparatus that is present in the range in which communication ispossible, and the power transmitting and receiving apparatuses canidentify each other.

Other Embodiments

Embodiments of the present invention can also be realized by a computerof a system or apparatus that reads out and executes computer executableinstructions recorded on a storage medium (e.g., non-transitorycomputer-readable storage medium) to perform the functions of one ormore of the above-described embodiments of the present invention, and bya method performed by the computer of the system or apparatus by, forexample, reading out and executing the computer executable instructionsfrom the storage medium to perform the functions of one or more of theabove-described embodiments. The computer may comprise one or more of acentral processing unit (CPU), micro processing unit (MPU), or othercircuitry, and may include a network of separate computers or separatecomputer processors. The computer executable instructions may beprovided to the computer, for example, from a network or the storagemedium. The storage medium may include, for example, one or more of ahard disk, a random-access memory (RAM), a read only memory (ROM), astorage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™,a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2013-088880, filed Apr. 19, 2013, which is hereby incorporated byreference herein in its entirety.

The invention claimed is:
 1. A power receiving apparatus comprising: anantenna configured to wirelessly receive power from a power transmittingapparatus; and one or more processors configured to: transmit, using afirst communication method, a first signal including address informationof the power receiving apparatus; transmit, using a second communicationmethod, a second signal including the address information that isincluded in the first signal; receive, using the second communicationmethod, a third signal from a power transmitting apparatus that receivesthe first signal including the address information and the second signalincluding the address information.
 2. The power receiving apparatusaccording to claim 1, wherein the first signal includes informationrepresenting that a wireless power transmission service is supported. 3.The power receiving apparatus according to claim 1, wherein the one ormore processors are further configured to receive, using the firstcommunication method, a fourth signal including the address informationof the power transmitting apparatus.
 4. The power receiving apparatusaccording to claim 3, wherein the one or more processor are furtherconfigured to receive, using the second communication method, a fifthsignal including the address information included in the fourth signal.5. The power receiving apparatus according to claim 1, wherein theaddress information is a BLUETOOTH® address.
 6. The power receivingapparatus according to claim 1, wherein a power reception parameterincluding information representing requested power is communicated withthe power transmitting apparatus using the second communication methodafter the third signal is received.
 7. The power receiving apparatusaccording to claim 1, wherein the first communication method is acommunication method using load modulation, and the second communicationmethod is a communication method according to BLUETOOTH® standard. 8.The power receiving apparatus according to claim 1, wherein the thirdsignal comprises a random number.
 9. The power receiving apparatusaccording to claim 8, wherein the random number is generated by thepower transmitting apparatus.
 10. The power receiving apparatusaccording to claim 1, wherein the third signal is a signal to establisha communication connection.
 11. The power receiving apparatus accordingto claim 1, wherein the address information is a MAC address.
 12. Thepower receiving apparatus according to claim 1, wherein the addressinformation is information to identify the power receiving apparatus.13. A communication method for a power receiving apparatus configured towirelessly receive power from a power transmitting apparatus, the methodcomprising: transmitting, using a first communication method, a firstsignal including address information of the power receiving apparatus;transmitting, using a second communication method, a second signalincluding the address identification information included in the firstsignal; receiving, using the second communication method, a third signalfrom the power transmitting apparatus that receives the first signalincluding the address information and the second signal including theaddress information.
 14. A non-transitory computer-readable storagemedium storing a program for causing a computer to execute acommunication method for a power receiving apparatus configured towirelessly receive power from a power transmitting apparatus, the methodcomprising: transmitting, using a first communication method, a firstsignal including address information of the power receiving apparatus;transmitting, using a second communication method different from thefirst communication method, a second signal including the addressinformation included in the first signal; receiving, using the secondcommunication method, a third signal for establishing a communicationconnection from the power transmitting apparatus that receives the firstsignal including the identification information and the second signalincluding the identification information.